There are a lot of different reasons that people hate Ubuntu. Most of them Not great reasons.
Ubuntu became popular by making desktop Linux approachable to normal people. Some of the abnormal people already using Linux hated this.
In November 2010, Ubuntu switched from GNOME as their default desktop to Unity. This made many users furious.
Then in 2017, Ubuntu switched from Unity to Gnome. This made many users furious.
There’s also a graveyard of products and services that infuriated users when canonical started them, then infuriated users when they discontinued them.
And the Amazon “scandal”.
And then there’s the telemetry stuff.
Meanwhile. Arch has always been the bad boy that dares you to love him… unapproachable and edgy.
I can’t speak for anyone else but I can tell you what I personally love about Gnome.
I like that it’s Spartan. I like that it looks good without me having to customize a thousand different settings.
I like that It has client side decorations, so every window doesn’t have to have an obscene, chunky, mostly useless title bar.
I don’t miss every single application having 100 different options packed into a menu bar. Once you get used to it, you realize that it was mostly getting in the way the whole time.
It’s just a really streamlined workflow for 98% of what you do. The problem is that 2% where it’s too spartan and God do you wish you had some options.
But I also think KDE is a great desktop environment. If I were more of a gamer I’d be using KDE. I think XFCE is an excellent desktop environment for aging hardware and Windows converts. It is very much a matter of taste, Use cases, and your preferred workflow.